1. Field of the Invention
This invention relates to novel genes encoding polypeptides that comprise a component of the telomerase enzyme complex, as well as to methods of making the genes and polypeptides.
2. Related Art
Many physiological changes occur as humans age. In addition to those observed at the phenotypic level such as change in hair color, appearance of skin, decreased lean body mass, etc., there are many changes at the cellular and biochemical levels. One such change that has been observed is a marked decrease in the length of telomeres in somatic cells as they age (Harley et al., Nature, 345:458-460 [1990]). Telomeres are repetitive DNA sequences that are localized to the ends of every chromosome, and are necessary for proper chromosome maintenance, replication, and localization of the chromosomes within the cell nucleus.
In most organisms, telomeres are synthesized and maintained by an enzyme known as telomerase. Telomerase is a ribonucleoprotein composed of RNA and protein components, and both types of components are necessary for activity (see for example, Greider, Annu. Rev. Biochem., 65:337-365 [1996]; Greider et al., in Cellular Aging and Cell Death, Wiley-Liss Inc., New York, N.Y., pp. 123-138 [1996]).
Most cells of adult humans do not have telomerase activity; exceptions include, for example, germline tissues (sperm cells and oocytes) and certain blood cells (Greider et al., Cellular Aging and Cell Death, supra). Decreased telomere length correlates well with decreased replicative capacity of cells in culture (referred to as cellular senescence or cell age). It has been postulated that shortened telomeres may be involved in the inability of cells to continue dividing (Harley, supra; Levy et al., J. Mol. Biol., 225:951-960 [1992]; and Harley et al., Cold Spring Harbor Symposium on Quantitative Biology, 59:307-315 [1994]), thereby contributing to senescence of the cells.
Recently, it has been shown that the telomeres of one class of white blood cells, called CD28-/CD8+ T-cells, are significantly shorter in AIDS patients as compared with the same cells obtained from healthy persons of the same or similar age (Effros et al., AIDS, 10:17-22 [1996]).
In many human cancerous cells, it has been shown that telomere length does not decrease, and telomerase activity is present, regardless of the age of these cells (Kim et al., Science, 266:2011-2015 [1994]; and Counter et al., EMBO J., 11:1921-1929 [1992]). It has been suggested that inhibition of telomerase in cancer cells might serve to decrease the proliferation of these cells (Harley et al., Cold Spring Harbor Symposium on Quantitative Biology, supra; and Greider et al., Cellular Aging and Cell Death, supra).
The RNA component of telomerase in several mammals has been cloned and sequenced (see PCT patent application WO 96/01835, published Jan. 25, 1995; Blasco et al., Science, 269:1267-1270 [1995]; Feng et al., Science, 269:1236-1241 [1995]), and it has been demonstrated that this RNA component is necessary for telomerase activity (Blasco et al., supra; Feng et al., supra; oral presentations at Cold Spring Harbor Laboratory Conference on Telomeres and Telomerase, Nov. 3-6 1996). In mouse tumor models, an increase in telomerase RNA correlates with increased tumor progression (Blasco et al., Nature Genetics, 12:200-204 [1996]). However, Avilion et al. (Cancer Res., 56:645-650 [1996]) showed that the presence of telomerase RNA in various human tumor tissues and cell lines was not a good predictor of the presence or amount of telomerase activity in these tissues and cell lines.
In ciliates (single celled eukaryotic organisms), it has been found that the protein portion of telomerase is comprised of two distinct polypeptides, termed p80 and p95 (see PCT patent application WO 96/19580, published Jun. 27, 1995; Harrington et al., J. Biol. Chem, 270:8893-8901 [1995]; and Collins et al., Cell, 81:677-686 [1995]). Recently, two telomerase polypeptides of molecular weight 120 kDa and 43 kDa have reportedly been purified in Euplotes, a single-celled eukaryotic organism (Lingner et al., Proc. Natl. Acad. Sci. USA, 93:10712-10717 [1996]). Prior to the present invention, the protein component or components of mammalian telomerase had not been identified.
Recently, a 347 base pair nucleic acid molecule was deposited in the public database Genbank as accession number H33937. This nucleic acid molecule was apparently identified from rat PC-12 cells that had been treated with NGF (neurotrophic growth factor). No function for this nucleic acid molecule or the protein encoded by it is set forth in the Genbank database information, however, a portion of this molecule has been found to be highly homologous to a region of the mouse telomerase RNA interacting protein 1 (TRIP1) of the present invention.
In view of the devastating effects of cancer and AIDS, there is a need in the art to identify molecules in the human body which may have an important role in the etiology of these diseases, and to manipulate the expression of such molecules in patients suffering from these and related diseases.
Accordingly, it is an object of this invention to provide nucleic acid molecules and polypeptides that affect aging and/or proliferation of cells in the human body.
It is a further object to provide methods of altering the level of expression of such nucleic acid molecules and polypeptides in the human body.
Other related objects will readily be apparent from a reading of this disclosure.